Nanohybridized Synthesis of Metal Nanoparticles and Their Organization

Abstract

Metal nanoparticles have various unusual chemical and physical properties compared with those of metal atoms or bulk metal due to the quantum size effect and their large superficial area, which make them attractive for applications such as optics, electronics, catalysis, and biology [1, 2]. The catalytic properties of metal nanoparticles have generated great interest over the past decade. Among various metal nanoparticles, gold nanoparticles have tremendously high molar absorptivity in the visible region. Particle aggrega-tion results in further color changes of gold nanoparticles solutions due to mutually induced dipoles that depend on interparticle distance and aggregate size. This phenomenon can be applied to various sensing systems [3-7]. The assembly of gold, silver, or copper nanoparticle monolayers is one of the ideal substrate for surfaced-enhanced Raman scattering (SERS) [8, 9]. Bare metal nanoparticles are prepared by employing physical methods such as mechanic subdivision of metallic aggregates and evaporation of a metal in a vacuum by resistive heating or laser ablation. Chemical methods such as the reduction of metal salts in solution are the most convenient ways to control the size of the particles and modified the surface chemical composition. To exploit nanoparticle properties for future device fabrication , self-organization of nanoparticles in a controlled manner is required. To construct such devices, new fabrication techniques must be developed with suitable metal nanoparticle-based building blocks. Several patterns for self-assemblies of the metal nanoparticles are schematically illustrated in Fig. 1.1. A number of outstanding reviews on the synthesis and assembly of metal nanoparticle-based building blocks have appeared [2, 10]. This chapter highlights recent fabrication techniques of hybrid metal nanoparticles by controlled self-organization of the metal nanoparticle-based building blocks. Design of nanoparticle hybrids will be first focused on using building blocks for further assemblies. Several recent efforts have been concentrated on a system that